This invention generally relates to the field of image processing and in particular to devices for capturing image data information as it is written on a surface.
Various systems have been proposed in the past for capturing image information as the information is written. Such systems typically detect forces that describe the pattern being traced out on a surface. These forces can be used to recreate the written image. How accurately written images can be recreated depends on how completely the forces describe the motion of the device against the surface. For example, forces acting on more than one axis of a pen point may represent that the pen point is moving along a writing surface, or may represent that the pen is being held at an angle on a stationary point. Without more information an accurate image cannot be obtained. The ability to image written information, therefore, is limited by the information concerning pen position and orientation.
For a device to accurately image information as it is written, data concerning the device's position on the writing surface, orientation to the writing surface and movement along the writing surface must be gathered.
In general, devices for imaging information as it is written gather information concerning movement by detecting the mechanical forces at the device's point while the point is in contact with the writing surface. In order to gather reasonably accurate information, imaging devices have typically employed special pen point cartridges for sensing mechanical forces. In many cases these pen point housings exhibit non-linear behavior, i.e. elastic compression, thereby corrupting the sensed data. Furthermore, these housings are costly and too fragile for a typical work environment.
In order to correctly process the forces sensed at a pen point, the orientation of the device to the surface must be known. For example, the device's ability to distinguish between forces caused by the pen point being held at an angle at a stationary spot and forces caused by the pen point being moved along a surface, cannot be resolved unless the orientation of the device is known. Devices for imaging written information have typically required that the pen point be held at a specific angle, usually perpendicular to the writing surface. While this method allows an accurate assessment of the forces when the pen point is held correctly, its accuracy falls off with slight variations of orientation and is therefore often impractical for the ordinary work environment.
Another consideration for imaging written information is the need to accurately position new images relative to prior images. Once a pen has been lifted from a writing surface its position relative to its prior location on the writing surface is unknown. Devices for imaging written information have typically required a special surface capable of detecting a pen point. While this method gathers pen point position data, it burdens the use of imaging devices and at the same time substantially increases cost.
It is, therefore, an object of the present invention to provide an imaging apparatus affording accurate representation of information as it is written on a surface.
It is another object of the present invention to provide such a device that operates accurately at the typical angular orientations of a conventional writing stylus.
It is a further object of the present invention to provide such a device that maintains absolute pen point position on a writing surface.
Further objects of the present invention will be apparent from the following detailed description.